Low-temperature selective hydrogenation of dienes



United States Patent 3,116,233 LOW-TEMPERATURE SELECTWE HYDROGENATION 0FDlENES Cornelia T. Douwes and Gterar dus J. F. Stijntjes, Amsterdarn,Netherlands, assignors to Shell Gil Company,

New York, N.Y., a corporation of Delaware No Drawing. Filed Dec. 30,1960,. Ser. No. 79,563

Claims priority, application Netherlands Jan. 14, 1960 8 Claims. (Cl.208-443) This invention relates to a process for the selectivehydrogenation of diene-containing hydrocarbon oils.

Products from the severe cracking of hydrocarbon oils ordinarily containsulfur compounds and considerable quantities of gum-forming dienes.Dienes in gasoline have a pronounced tendency to polymerize,particularly under the influence of air and light, to form gummymaterials which deposit upon feed lines, carburetors, valves and thelike when the fuel containing them in used in internal combustionengines and thus interferes with the proper operation thereof. Removalof the dienes by ordinary chemical and clay treating processes usuallyresults in large losses of valuable antiknock fuel ingreients. Removalof the gum-forming dienes by polymerization even under optimumconditions tends to result in volumetric losses up to about 20%.Therefore, a preferred method of securing stabilization of a crackedproduct is one wherein the diolefins are selectively hydrogenatedwithout substantial loss of fuel ingredients.

It is known to hydrogenate selectively a dienecontaining gasoline in thepresence of hydrogen at an elevated temperature over a catalystcomprising nickel supported on alumina. A catalyst comprising nickeldeposited on a carrier having lower cracking and polymerization activitythan gamma-alumina has also been proposed. The proposed carriers includethe oxides and carbonates of calcium, magnesium, strontium, and barium,silicon carbide, quartz, diatomaceous earth, carbon, and pumice.However, these catalysts are unsatisfactory from the standpoint ofactivity, mechanical strength, difficulty in preparation, and the like.For example, barium oxide is practically useless as a carrier since itpartially melts during catalyst preparation which thereby adverselyaffects the pore structure.

An object of this invention is to provide an improved method of treatingunstable light hydrocarbon oils which are difficult to refine byordinary chemical and clay treating processes without incurring largelosses of valuable ingredients. A further object of this invention is toprovide an improved method for improving the stability of adiene-containing gasoline by an improved selective hydrogenationtreatment. More particularly, the object of this invention is to providea process for improving the stability of diene-containing gasoline by alow temperature catalytic selective hydrogenation treatment.

It has now been found that the dienes and other highly reactiveunsaturated compounds such as occur in light hydrocarbon oils obtainedby cracking can be hydrogenated in a particularly selective manner toform alkenes by using a cobalt or nickel catalyst supported on an alkaliearth metal sulfate as carrier. Other favorable properties of theproduct are not adversely affected by this selective hydrogenation butare even improved in certain cases. By light cracked hydrocarbon oils itis meant hydrocarbon oils having a final boiling point (A.S.T.M.) of notmore than 375 C. which are obtained from cracking processes. Unstablevery reactive unsaturated compounds occur in relatively large quantitiesin gasolines and kerosines obtained by thermal cracking, particularly athigh temperatures and short contact time.

3,115,233 Patented Dec. 31, 1963 The present process is particularlysuitable for the treatment of gasoline or fractions thereof obtained bythermally cracking in the presence of steam a hydrocarbon oil with afinal boiling point of not more than approximately 250 C. Thesegasolines are extremely unstable owing to the presence of a relativelyhigh content of highly unsaturated hydrocarbons. However, thesegasolines have a very high octane rating owing to the high percentage ofaromatic compounds and alkenes which are in themselves stable motorgasoline components.

The highly unstable steam-cracked gasolines are produced by thermallycracking at a high temperature in the presence of steam, a hydrocarbonoil and preferably a hydrocarbon oil relatively rich in aliphatichydrocarbons. Cracking in the presence of steam is usually effected attemperatures between approximately 550 C. and 900 C., preferably between750 C. and 800 C., and generally under a pressure below approximately 5atm. abs. The quantity of steam employed is usually 0.1l0 parts byweight, preferably about 1 part by weight per part by weight of startingmaterial. Cracking in the presence of steam is mainly applied for thepreparation of lower alkenes, in particular ethene and propene, whichare used as starting materials in the chemical industry. During thecracking treatment, which is generally carried out in a pipe still,usually more than 50% by weight of the starting hydrocarbon oil isconverted into compounds having four or fewer carbon atoms in themolecule. The by-product formed during the cracking in the presence ofsteam is the gasoline which is refined by the process of the presentinvention and which usually contains more than 30% by weight and oftenmore than 60% by weight of aromatic compounds and has a considerablecontent of alkenes with a relatively high octane number. In addition, arelatively large amount of highly reactive compounds, mainly dienes,inter alia, those of the cyclopentadiene type, are present. It is alsoof advantage that in most cases these gasolines are. practically free ofsulfur, i.e. they have a content of sulfur compounds (calculated aselemental sulfur) which is considerably lower than 0.1% by weight. Thesegasolines usually contain little or no naphthenic hydrocarbons.

The process of the present invention enables the unstable compoundspresent in such gasolines to be converted into more saturated compoundsby means of selective hydrogenation, whereas the valuable alkenes arehardly, if at all, affected. The process of the invention is alsosuitable for use with other diene-containing gasolines such as thoseproduced from high temperature short contact catalytic or thermalcracking of gas oil fractions. The diene content of such gasolines,while appreciable, is usually less than that of steam-cracked fractions.Moreover, the process of the invention is suitable for lower boilinghydrocarbons such as a C fraction containing diolefins such asmethylacetylene and propadiene. Such low boiling fractions may betreated per se or combined with diolefin-containing gasolines in theprocess of the invention.

The course of the present hydrogenation is greatly affected by thenature of the carrier on which the nickel or cobalt catalyst issupported. It was found that the use of alkaline earth metal sulfates ascarrier gave surprisingly suitable catalysts with which particularlyselective hydrogenations could be carried out. The alkaline earth metalsulfates can be employed as such or in the form of mixtures with othercarrier materials. Only those alkaline earth metal sulfates which areinsoluble or substantially insoluble in water are suitable for use as acarrier since the catalyst is usually prepared by impregnating thecarrier with an aqueous nickel or cobalt salt solution. In such a case aWater-soluble alkaline earth metal sulfate,

for example magnesium sulfate, is manifestly unsuitable since thestructure, which is very important for the action of the catalyst, willbe affected during the impregnation treatment by the partial dissolutionof the alkaline earth metal sulfate. Moreover, such water-solublecarriers, even should the nickel component be deposited by means otherthan aqueous solutions, would be unsuitable for use withWater-containing feeds or would require expensive means to dehydrate thefeed.

The nickel or cobalt component of the catalyst is deposited on thecarrier in an amount (calculated as metal) from about 1% to about 25% byweight, and preferably from 3% to 10% by weight, based on the totalcatalyst.

The selective hydrogenation is carried out at average catalysttemperatures of not more than about 160 C. and preferably at averagetemperatures in the range of from 70 C. to 130 C.

To ensure satisfactory hydrogenation a quantity of hydrogen is employedwhich is at least equal to the theoretical responding alkene. In orderto maintain the activity of the catalyst over longer periods, however,it is preferred to use 2-5' times the theoretical amount of hydrogen.

The gas employed may be hydrogen or a hydrogen-containing gas mixture,for example a mixture of hydrogen and light hydrocarbons.

The gases employed should preferably contain more than 60% by volume ofhydrogen. Very suitable are, for example, the hydrogen-containing gasesobtained in the catalytic reforming of gasoline fractions.

The liquid hourly space velocity is usually 0.05-5 kg. and preferably 13kg. of hydrocarbon per hour per liter of catalyst. The gas/hydrocarbonoil ratio is usually between 50 and 300 liters (standard temperature andpressure) of gas per kg. of hydrocarbon oil.

Although according to the by weight and preferably as to more than 75%by weight, in the liquid phase without the need for excessively highpressures, trickle technique is particularly suitable for this pur-According to this technique which is described in ,608,521 (issuedAugust 26, 1952), the startprocess of the invention wherein temperatureis not more than 160 C., hydrogenation in the liquid phase usuallyproceeds at pressures between and '60 atm. abs., preferably between and40* atm. abs. Because of the exothermic nature of the hydrogenatingreactions there The starting material used was a gasoline obtained as abyproduct in the preparation of ethene and propene by cracking in thepresence of steam a straight-run hydrocarbon oil having a final boilingpoint of 230 C. This gasoline was free of naphthenic hydrocarbons andcontained 11% by weight of dienes, 10% by weight of alkenes, about 36%by weight of aromatic hydrocarbons and about 43% by weight saturatedhydrocarbons. The sulfur content was less than 0.01% by weight. Becauseof the high diene content, the gasoline was very unstable, as shown byan induction period of only about 9 minutes without the addition of aninhibitor.

Other properties of the gasoline were: boiling range 41 C.180 C.(A.S.T.M.); McIlhiney bromine number 52 g./ 100 g.; and an Ellis andJones maleic anhydride number of 112 mg./g. When all the unsaturated compounds were completely saturated the hydrogen consumption was liters(S.T.P.) per kilogram of oil.

The gasoline, substantially in a liquid state and in the presence of 200liters (S.T.P.) of hydrogen per kilogram of gasoline, was passed overthe catalyst (3 x 3 mm. pellets) at an average catalyst temperature ofC., a pressure of 40 atm. abs. and a liquid hourly space velocity of 2kg. of gasoline per hour per liter of catalyst.

Under these conditions three experiments were conducted in which thecatalysts used were:

Catalyst Anickel supported on barium sulfate (nickel content 4.8% w.)

Catalyst B-nickel supported on barium carb0nate( nickel content 4.8% w.)

Catalyst C-nickel supported on barium carbonate (nickel content 10.0%w.)

The catalysts were prepared as follows. The carrier material wasimpregnated by mixing it in powder form with a nickel nitrate solutionto form'a paste. To this end the barium sulfate was zixed with a nickelnitrate solution containing 7.5% by weight of nickel (calculated asmetal) and the barium carbonate powder was mixed with nickel nitratesolutions containing 5% by weight and 10% by weight of nickelrespectively. After separating the excess water, the resultant materialwas dried at 120 C. and then compressed with stearic acid as lubricantto form 3 x 3 mm. pellets. The stearic acid was burned off in thepresence of oxygen and the catalyst was then calcined at 500 C. Finallya reduction treatment was carried out by passing over the catalysthydrogen at a rate of 400 liters (S.T.P.) per hour per liter of catalystfor 3 hours at 400 C. and under a pressure of 40 atm. abs. Catalyst Dwas prepared by mixing barium sulfate powder with a cobalt nitratesolution containing 48% by weight cobalt (calculated as metal) to form apaste. This catalyst was dried, pelleted and tested with the same feedand under the same conditions as the nickel catalysts.

The data are given in the following Table I.

Table I HYDROGENATION OF UNSTABLE GASOLINE Specific gravity 0.75 0.750.76 0.76 O. romine number. g./l00 g 52 19 48 Maleie acid anhydridenumber 112 8. 9 94 107 3G Hydrogen consumption [liters (S. T. P.)

per kg. of gasoline] 50 1 6 7 Weight ratio of conjugated alka enes:

alkenes 99 2 62 110 15 F-1-1V octane number 99. 5 98. 0 99. 2 99. 0 99.0 F21% octane number 84. 4 87. 5 84. 8 84. 5 85. 2

for the hydrogen consumption and the decrease in the maieic acidnhydriue number, which is a measure of the alkadiene content and thestability of the resultant product. The selectivity is indicated by thefigure showing the ratio of the quantity of conjugated alkadienes tothat of the alltenes. The lower this figure, the relatively larger isthe quantity of alkadienes hydrogenated and the amount of unconvertedalkenes which are important for the octane number of the gasoline.

It should be noted also that the sensitivity of the gasoline is greatlyimproved by the selective hydrogenation over nickel supported on bariumsulfate, whereas it is little aifected by the other catalysts. The termsensitivity is a measure of the sensitivity of the gasoline to changesin the operating conditions of the engine and is determined as thedifference between the E-l and F2 octane rating. A low sensitivity isdesired in gasolines for the modern high-compression ratio engines, andparticularly a low sensitivity gasoline with a high Fl rating. Thebarium sulfate supported catalyst was particularly effective in thisrespect in that the E-2 rating was raised from 84.7 to 87.5.

We claim as our invention:

1. A process for the selective hydrogenation of themcontaining gasolineswhich comprises contacting said gasoline with hydrogen at a temperatureof about 70 to about 130 C. in the presence of a catalyst comprising awater-insoluble alkaline earth metal sulfate on which is deposited ametal selected from the group consisting of nickel and cobalt.

2. A process for the selective hydrogenation of dienecontaininggasolines which comprises contacting said gasoline with a gas containingat least 60% by volume hydrogen at a temperature of from about 70 toabout 130 C. in the presence of a catalyst comprising from 1% to about25% by weight of nickel deposited on a water-insoluble alkal e earthmetal sulfate.

3. The process according to claim 2 wherein the gaso line has a sulfurcontent, calculated as elemental sulfur, of less than 0.1 by weight.

4. A process for the selective hydrogenation of dienecontaininggasolines which comprises contacting said gasoline with a gas containingat least 60% by volume hydrogen in the presence of a catalyst comprisingfrom 1% to about 25% by weight nickel deposited on a waterinsolublealkaline earth metal sulfate, said selective hydrogenation being carriedout at a temperature of from about 70 to about 130 C., a pressure ofbetween and 60 atmospheres absolute, a liquid hourly space velocity of0.5-5 kilograms of gasoline per hour per iter of catalyst, and a gas togasoline ratio of 50300 liters (measured at standard temperature andpressure) of gas per :ilogram of gasoline.

5. A process for the selective hydrogenation of dienecontaininggaaolines which comprises contacting said gasoline with a gas containingat least 60% by volume hydrogen in the presence of a catalyst comprisingfrom 3% to 10% by weight nick l deposited on barium sulfate, saidselective hydrogenation being cm'ried out at a temperature of from about70 to about 130 C., a pressure between 20 and 40 atmospheres absolute, aliquid hourly space velocity of 1.03.0 kilograms of gasoline per hourper liter of catalyst, a hydrogen to gasoline ratio of 300 liters(measured at standard tern erature and pressure) of hydrogen perkilogram of gasoline.

6. A process for the selective hydrogenation of theirscontaininggasolines which comprises contacting said gasoline with a gas containingat least by volume hydrogen at a temperature of from about to about C.in the presence of catalyst comprising from to about 25% by weight ofcobalt deposited on a waterinsoluble alkaline earth metal sulfate.

7. A process for the selective hydrogenation of dienecontaininggasolines which comprises contacting said gasoline with a gas containingat least 60% by volume hydrogen in the presence of a catalyst comprisingfrom 1% to about 25% by weight cobalt deposited on a waterinsolublealkaline earth metal sulfate, said selective hydrogenation being carriedout at a temperature of from about 70 to about 130 C., a pressure ofbetween 10* and 60 atmospheres absolute, a liquid hourly space velocityof 0.5-5 kilograms of gasoline per hour per liter of catalyst, and a gasto gasoline ratio on? 50-300 liters (measured at standard temperatureand pressure) of gas per kilogram of gasoline.

8. A process for the selective hydrogenation of alienscontaininggasolines which comprises contacting said gasoline with a gas containingat least 60% by volume hydrogen in the presence of a catalyst comprisingfrom 3% to 10% by weight cobalt deposited on barium sulis c, saidselective hydrogenation being carried out at a temperature of from about70 to about 130 C., a pressure between 20 and 4-0 atmospheres absolute,a liquid hourly space velocity of 1.0-3.0 kilograms of gasoline per hourper liter of catalyst, a hydrogen to gasoline ratio of 50300 liters(measured at standard temperature and pressure) or hydrogen per kilogramof gasoline.

References Eiterl in the file of this patent UNITED STATES PATENTS2,588,359 Chitwood et a1. Mar. 11, 1952 2,810,004 Morbeck et al Oct. 15,1957 2,861,946 Sage et a1. Nov. 25, 1958 2,878,180 Watkins m. Mar. 17,1959

1. A PROCESS FOR THE SELECTIVE HYDROGENATION OF DIENECONTAININGGASOLINES WHICH COMPRISES CONTACTING SAID GASOLINE WITH HYDROGEN AT ATEMPERATURE OF ABOUT 70* TO ABOUT 130*C. IN THE PRESENCE OF A CATALYSTCOMPRISING A WATER-INSOLUBLE ALKALINE EARTH METAL SULFATE ON WHICH ISDEPOSITED A METAL SELECTED FROM THE GROUP CONSISTING OF NICKEL ANDCOBALT.